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31 There a two primary types of radix-based sorting:
34 Most-significant-digit Radix sorting (MSD) divides the data recursively
35 based upon the top-most unsorted bits. This approach is efficient for
36 even distributions that divide nicely, and can be done in-place (limited
37 additional memory used). There is substantial constant overhead for
38 each iteration to deal with the splitting structure. The algorithms
39 provided here use MSD Radix Sort for their radix-sorting portion. The
40 main disadvantage of MSD Radix sorting is that when the data is cut
41 up into small pieces, the overhead for additional recursive calls starts
42 to dominate runtime, and this makes worst-case behavior substantially
43 worse than <span class="emphasis"><em>𝑶(N*log(N))</em></span>.
46 By contrast, <code class="literal"><code class="computeroutput"><a class="link" href="../../../../../boost/sort/spreadsort/integer__idm46048203222928.html" title="Function template integer_sort">integer_sort</a></code></code>,
47 <code class="literal"><code class="computeroutput"><a class="link" href="../../../../../boost/sort/spreadsort/float_so_idm46048204416688.html" title="Function template float_sort">float_sort</a></code></code>,
48 and <code class="literal"><code class="computeroutput"><a class="link" href="../../../../../boost/sort/spreadsort/string_s_idm46048202990736.html" title="Function template string_sort">string_sort</a></code></code>
49 all check to see whether Radix-based or Comparison-based sorting have
50 better worst-case runtime, and make the appropriate recursive call.
51 Because Comparison-based sorting algorithms are efficient on small
52 pieces, the tendency of MSD <a href="http://en.wikipedia.org/wiki/Radix_sort" target="_top">radix
53 sort</a> to cut the problem up small is turned into an advantage
54 by these hybrid sorts. It is hard to conceive of a common usage case
55 where pure MSD <a href="http://en.wikipedia.org/wiki/Radix_sort" target="_top">radix
56 sort</a> would have any significant advantage over hybrid algorithms.
59 Least-significant-digit <a href="http://en.wikipedia.org/wiki/Radix_sort" target="_top">radix
60 sort</a> (LSD) sorts based upon the least-significant bits first.
61 This requires a complete copy of the data being sorted, using substantial
62 additional memory. The main advantage of LSD Radix Sort is that aside
63 from some constant overhead and the memory allocation, it uses a fixed
64 amount of time per element to sort, regardless of distribution or size
65 of the list. This amount of time is proportional to the length of the
66 radix. The other advantage of LSD Radix Sort is that it is a stable
67 sorting algorithm, so elements with the same key will retain their
71 One disadvantage is that LSD Radix Sort uses the same amount of time
72 to sort "easy" sorting problems as "hard" sorting
73 problems, and this time spent may end up being greater than an efficient
74 <span class="emphasis"><em>𝑶(N*log(N))</em></span> algorithm such as <a href="http://en.wikipedia.org/wiki/Introsort" target="_top">introsort</a>
75 spends sorting "hard" problems on large data sets, depending
76 on the length of the datatype, and relative speed of comparisons, memory
77 allocation, and random accesses.
80 The other main disadvantage of LSD Radix Sort is its memory overhead.
81 It's only faster for large data sets, but large data sets use significant
82 memory, which LSD Radix Sort needs to duplicate. LSD Radix Sort doesn't
83 make sense for items of variable length, such as strings; it could
84 be implemented by starting at the end of the longest element, but would
85 be extremely inefficient.
88 All that said, there are places where LSD Radix Sort is the appropriate
89 and fastest solution, so it would be appropriate to create a templated
90 LSD Radix Sort similar to <code class="literal"><code class="computeroutput"><a class="link" href="../../../../../boost/sort/spreadsort/integer__idm46048203222928.html" title="Function template integer_sort">integer_sort</a></code></code>
91 and <code class="literal"><code class="computeroutput"><a class="link" href="../../../../../boost/sort/spreadsort/float_so_idm46048204416688.html" title="Function template float_sort">float_sort</a></code></code>.
92 This would be most appropriate in cases where comparisons are extremely
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